LTE (Long Term Evolution) is a communication standard realizing a speed faster than those based on the third-generation mobile phone communication standards. LTE is being formulated by a standardization organization 3GPP. In a communication system adopting LTE (LTE system), most of the data between a base station and a mobile station is sent and received through two shared channels of a physical uplink shared channel (PUSCH) corresponding to an uplink and a physical downlink shared channel (PDSCH) corresponding to a downlink. Based on data transmission and reception through such shared channels, the base station executes scheduling (allocation of any of shared channels to any of mobile stations for communication) for an uplink and for a downlink. Scheduling is executed per subframe independently for an uplink and for a downlink (see Patent Documents 1 and 2, for example). The base station uses a control channel referred to as a physical downlink control channel (PDCCH) to notify each mobile station of scheduling information representing results of each scheduling. The PDCCH includes information elements referred to as downlink control information (DCI) based on scheduling information and is mapped in a subframe in a frame. The base station notifies each mobile station of the PDCCH.
Patent Document 1:
Japanese Patent Kokai Publication No. JP2008-172356A
Patent Document 2:
Japanese Patent Kokai Publication No. JP2008-172366A
The entire disclosures of the above Patent Documents are incorporated herein by reference thereto. The following analyses are given by the present invention.
The number of DCI items allocatable to a single subframe is limited and the DCI is shared by an uplink and a downlink. Thus, it is necessary to balance the number of DCI items allocated to each of the uplink and the downlink. However, when scheduling for an uplink and scheduling for a downlink are executed independently at different process timings information cannot be shared, in which the number of DCI items cannot be changed dynamically. As a result, the DCI cannot be allocated efficiently, counted as a problem.
It is a primary object of the present invention to provide a base station, a communication system, and a communication control method that efficiently allocate control information based on scheduling.
According to a first aspect of the present invention, there is provided a base station that executes scheduling for an uplink and scheduling for a downlink per subframe to communicate with mobile stations, the base station comprising: a control information item number estimation unit that estimates the number of control information items usable for the uplink and the number of control information items usable for the downlink per subframe; and a scheduling unit that executes scheduling for the uplink and scheduling for the downlink per subframe by using a number of control information items usable for the uplink and a number of control information items usable for the downlink, the numbers estimated by the control information item number estimation unit.
It is preferred that the base station according to the present invention comprise: a mobile station information management unit managing information about uplink data and downlink data for each of the mobile stations; and a common control information management unit managing common control information. In addition, It is preferred that the control information item number estimation unit by using information from the mobile station information management unit that estimates the number of control information items usable for the uplink and the number of control information items usable for the downlink per subframe and common control information from the common control information management unit.
Based on the base station according to the present invention, It is preferred that the scheduling unit comprise: an uplink scheduling unit that executes scheduling for the uplink per subframe by using the number of control information items usable for the uplink estimated by the control information item number estimation unit and information about uplink data managed by the mobile station information management unit; and a downlink scheduling unit that executes scheduling for the downlink per subframe by using the number of control information items usable for the downlink estimated by the control information number estimation unit and information about downlink data managed by the mobile station information management unit.
Based on the base station according to the present invention, It is preferred that, after receiving scheduling information representing results of scheduling for the downlink from the downlink scheduling unit, the uplink scheduling unit execute scheduling for the uplink.
Based on the base station according to the present invention, It is preferred that, after receiving scheduling information representing results of scheduling for the uplink from the uplink scheduling unit, the downlink scheduling unit execute scheduling for the downlink.
Based on the base station according to the present invention, It is preferred that, when the uplink scheduling unit and the downlink scheduling unit complete respective scheduling processes in a previous subframe, the mobile station information management unit update information about uplink data and downlink data in a next subframe.
Based on the base station according to the present invention, It is preferred that the control information be DCI and that the base station comprise a PDCCH generation unit generating a downlink PDCCH including DCI, based on scheduling information representing results of scheduling from the scheduling unit.
Based on the base station according to the present invention, It is preferred that the control information be CCE and that the base station comprise a PDCCH generation unit generating downlink PDCCH including CCE, based on scheduling information representing results of scheduling from the scheduling unit.
According to a second aspect of the present invention, there is provided a communication system comprising the base station as aforementioned and a mobile station that can communicate with the base station.
It is preferred that the communication system according to the present invention be an LTE system adopting LTE.
According to a third aspect of the present invention, there is provided a communication control method executed in a base station executing scheduling for an uplink and scheduling for a downlink per subframe to communicate with mobile stations. The method comprises: estimating a number of control information items usable for the uplink and a number of control information items usable for the downlink per subframe; and using the estimated number of control information items usable for the uplink and the estimated number of control information items usable for the downlink to execute scheduling for the uplink and scheduling for the downlink per subframe.
Based on the communication control method according to the present invention, It is preferred that, in the estimating the numbers, the number of control information items usable for the uplink and the number of control information items usable for the downlink per subframe be estimated by using information about uplink data and downlink data for each of the mobile stations and common control information.
Based on the communication control method according to the present invention, in the executing scheduling. It is preferred that scheduling for the uplink be executed per subframe by using the estimated number of control information items usable for the uplink and the information about uplink data and that scheduling for the downlink be executed per subframe by using the estimated number of control information items usable for the downlink and the information about downlink data.
Based on the communication control method according to the present invention, It is preferred that, in the executing scheduling, after scheduling information representing results of scheduling for the downlink is received, scheduling for the uplink be executed.
Based on the communication control method according to the present invention, It is preferred that, in the executing scheduling, after scheduling information representing results of scheduling for the uplink is received, scheduling for the downlink be executed.
It is preferred that the communication control method according to the present invention comprise updating information about uplink data and downlink data in a next subframe when a scheduling process for the uplink and a scheduling process for the downlink in a previous subframe are completed.
Based on the communication control method according to the present invention, It is preferred that the control information be DCI and that the method comprise generating a downlink PDCCH including DCI based on scheduling information representing results of the scheduling.
Based on the communication control method according to the present invention, It is preferred that the control information be CCE and that the method comprise generating a downlink PDCCH including CCE based on scheduling information representing results of the scheduling.
According to a fourth aspect of the present invention, there is provided a program causing a base station to execute the communication control method aforementioned. The program may be embodied in a computer readable, non-transient recording medium.
According to the present invention, a base station executes scheduling for an uplink and scheduling for a downlink per subframe, by using an estimated number of control information items usable for the uplink and for the downlink. In this way, even if scheduling for the uplink and scheduling for the downlink are independently executed at different timings, allocation of the control information based on scheduling information can be executed efficiently.